Many materials handling industries, and particularly the food processing industry, often use a device referred to as a scraped surface heat exchanger. A scraped surface heat exchanger generally features a tubular outer housing which surrounds a rotating central shaft. The rotating central shaft has hingedly connected paddles or blades that extend angularly radially outward and contact the inside surface of the outer housing as the central shaft rotates. The outer housing has a material inlet at one end and a material outlet at the other end and the material being processed is pumped through so that it passes along the length of the heat exchanger from the inlet to the outlet.
The outer housing is typically heated or cooled so that the material will undergo a change of temperature as it passes through the scraped surface heat exchanger. Further, the paddles or blades help agitate the material and/or scrape it off the inside surface of the heat exchanger as desired.
Since the scraped surface heat exchanger essentially has a single longitudinal rotating central shaft that rotates within a fixed longitudinal cylindrical housing, it is typical to suspend the shaft at each end of the housing via a roller or ball bearing arrangement at the end caps of the housing at each end of the shaft and each respective end of the housing. It is typically desirable to provide a seal so that the material does not come into contact with these roller bearings. Providing such a seal between the shaft and the housing is desirable to isolate the bearings from the material so that the bearings do not become clogged, to permit lubrication of the bearings, and/or to permit cleaning of the bearings by separating the bearings from the material. Further, preventing the food product from contacting the bearings also enhances the cleanliness of the food product so that it is not contaminated by materials associated with the bearings.
The known sealing arrangements for sealing between the inside of the housing from the rotating central tube have some disadvantages, however, in particular, due to cleanliness restrictions and regulations that are particularly imposed when the scraped surface heat exchanger is used for food-based applications, sanitary requirements often require that the shaft be removed and all the sealed components cleaned with substantial frequency in some cases even daily.
Scraped surface heat exchangers are generally fairly long tubes, for example 3–6 feet long, and to save the floor space each one occupies in a facility, they are often vertically mounted. The disassembly of most known seals for the removal of the shaft and seal components for cleaning, generally requires that both the end caps of the heat exchanger be removed. For vertically mounted units, this requires an operator to reach up, or in some cases climb up, to the height of the top of the scraped surface heat exchanger each time such a disassembly and cleaning process is to be performed. This can be cumbersome and time consuming, and also increases the risk that the operator will drop one of the loose parts from top of the heat exchanger during disassembly.
Accordingly, it would be desirable to have a seal assembly and method for a scraped surface heat exchanger wherein removal of the central tube and the cleanable seal components for both ends of the unit can be accomplished from only one end of the heat exchanger, which could be the lower end in vertically installed units.